The present invention relates in general to plug valves utilized in high pressure environments and more specifically to a high pressure valve having a valve body containing a plug allowing bi-directional flow and moveable between an open and closed flow-through position and a lubricating mechanism for introducing lubricant through the plug to a plug/insert interface or a plug/valve body interface regardless of the position of the plug in relation to the valve body.
Plug valves have been utilized in industry for many years and are very common in oil field service. Plug valves are commonly employed in heating and treating systems, cementing, fracturing and acidizing applications, blowout preventers and other applications and systems in which high working pressures are encountered. Conventional plug valves comprise a valve body having a fluid transmission conduit formed therethrough connectable to a transmission line, a plug member having a fluid conduit formed therethrough is rotatably disposed within the valve body in a manner that when the plug is in the open position fluid may pass through the plug valve and when in the closed position the plug fluid conduit is offset from the valve body fluid conduit and fluid is prevented from flowing therethrough. It is common for a valve insert to be positioned within the valve body between the valve body and the plug. The valve insert is typically constructed in two halves and the whole forms a conduit port aligned with the fluid conduit of the valve body.
Due to the high pressure and abrasive conditions experienced by plug valves it is necessary to lubricate the valve while in service. It is very detrimental to the safety of operators and to the operations to have a plug valve that cannot be readily opened or closed and/or that has excessive leakage around the valve/body or valve/plug interface.
Prior art plug valves have attempted to provide for frequent and effect lubricating and sealing of plug valves with limited success. A common solution has been to supply a lubricant through the valve body to a plug or split plug member having lubricating grooves formed on the surface. One of many problems with this design is that the lubricating ports from a lubricating reservoir in the valve body must be precisely aligned with grooves formed on the split valve plug. Any offset of these connections results in loss of lubricant and failure to adequately lubricate and seal the plug/valve body interface. Additionally, the utilization of a lubrication valve on the exterior of the valve body is a safety and environmental hazard. Reality shows that plug valves, as other equipment, are subjected to less than tender care. From transportation to installation through service and repair these plug valves are bounced around, hit, and thrown as if an inanimate object. This treatment often results in damage and loss of mechanical integrity of the lubricant insert. This loss of integrity often results in failure of the lubricant insert sending the device under extremely high pressure and high velocity away from the valve. At a minimum this ejection of the lubricant insert results in leakage of fluid from the system and possible shutdown of the system for replacement to, on the more serious side, the lubricant insert impacting or piercing an operator.
Another prior art plug valve as disclosed in U.S. Pat. No. 4,506,696 to van Pechmann utilizes a lubricant/sealant injection insert and lubricating/sealant conduits formed in the plug for communication with lubrication/sealant grooves formed in the valve insert. The design of the ""696 device, although complete in itself, does not adequately address the problems associated with plug valves. First, the ""696 patent teaches conduits formed through the plug to introduce a lubricant or sealant into a lubricating groove formed on the inside portion of the insert about the fluid passageway formed through the insert, therefore only allowing lubricating and/or sealing the valve when the plug is in the open position. Second, the lubricating grooves of the ""696 patent are formed on the inside of the insert and are in the flow path of the fluid when cycling the valve resulting in the lubricant being washed from the groove and wear on the groove resulting in ineffective lubricating and sealing over time. Additionally, the complicated manufacturing and assembly of inserts having internal grooves for lubricating is difficult, costly and often results in an inoperable plug.
It is thus desired to provide a plug valve that permits introduction of a lubricant through the plug into an interface between the plug and valve body or insert when the valve is in service and regardless of the position of the plug relative to the valve body. It is further desired to provide a plug valve that includes a lubricating port that is substantially shielded to protect a lubricating fitting from impact. It is still further desired to provide a lubricated plug valve that does not require additional machining or refurbishment of plug valve inserts.
In view of the foregoing and other considerations, the present invention relates to an apparatus and method of lubricating a plug valve when the valve is in service and regardless of the position of the plug relative to the valve body.
It is a feature of the present invention to provide a lubricated valve that does not require refurbishment or additional machining of plug valve inserts.
It is a further feature of the present invention to provide a lubricated valve wherein the plug has grooves formed on an outside surface thereof that surrounds the sealing area of the valve insert when the plug is in the closed position.
It is a still further feature of the present invention to provide a plug valve having lubricating port formed in the plug and shielded to protect a lubricating fitting from impact.
Accordingly, a method and apparatus for lubricating a plug valve is provided. The lubricated valve includes a valve body forming a fluid conduit therethrough having opposing end connections connected within a fluid flow line, the valve body forming a valve cavity formed substantially perpendicular to the axis of flow through the body fluid conduit and terminated by cavity openings formed through the valve body; a valve insert forming an insert bore formed therethrough positioned within the valve cavity in a manner such that the insert bore is aligned with the valve fluid conduit and a insert-body sealing interface is formed; a substantially cylindrical plug having a plug fluid conduit formed therethrough, at least one continuous lubricating groove formed on the outside surface of the plug located between the ends of plug fluid conduit, a lug extending from one end of the plug, and a lubricating port formed in the opposing end of the plug in fluid connection with the lubricating groove via a transverse lubricant channel and lateral lubricant channel formed by the plug, the plug being rotatably disposed within the insert with the lug extending through one of the cavity openings and the lubricating port accessible through the other cavity opening and forming a plug-insert interface, the plug moveable between an open position with the plug fluid conduit aligned with the body fluid conduit to a closed position wherein the plug fluid conduit is offset from the body fluid conduit; a securing device having a securing device cavity for maintaining the plug and the insert in the valve body, the securing device disposed in the cavity opening wherein the lubricating port is positioned within the securing device cavity; and means for introducing lubricant through the plug via the plug port and the channels to the lubricating groove positioned at the plug-insert interface when the plug is in the closed position, and the lubricating groove is positioned proximate a relief area formed by the insert when the plug is in the open position.
The lubricated plug valve may include a pair of lubricating grooves the grooves formed on the outside surface of the plug on opposing sides of the plug between the ends of the plug fluid conduit.
A method of lubricating an in-service plug valve includes the steps of: rotating a plug having plug fluid conduit within a valve body and insert to an open position so that said plug conduit is aligned with a valve body fluid conduit permitting fluid to pass through said valve body; introducing a lubricant through the plug to a lubricating groove and into a relief area formed by the insert when the plug is in the open position; rotating the plug to a closed position wherein the plug conduit is offset from the valve body fluid conduit blocking fluid flow through the valve body; and introducing lubricant through the plug to a lubricating groove positioned at a plug-insert interface when the plug is in the closed position.
The foregoing has outlined the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention.